1. Technical Field
The present invention relates generally to metal diaphragm regulators. More specifically, the present invention relates to a metal diaphragm structure for pressure regulators for increasing flow capacity, flow control, and pressure rating.
2. Background Information
Metal diaphragm regulators have been in use for years. Typically, metal diaphragm regulators include a flexible metal diaphragm clamped between a body section, and an actuator section.
The body section typically has at least one inlet, or high pressure fluid port and at least one outlet, or low pressure or regulated fluid port. A poppet valve, seat, and bias spring are typically contained within the body section. The poppet valve and seat separate the high pressure from the low regulated pressure. The bias spring biases the poppet valve against the seat enabling a positive fluid shut-off.
The actuator section, which usually contains an adjustably loaded compression spring commonly referred to as a xe2x80x98rangexe2x80x99 spring, applies a downward reference force upon the upper surface of the diaphragm. This causes the diaphragm to deflect, engaging the poppet valve away from its valve seat and allowing fluid flow and pressure to build on the low-pressure side. The greater the deflection, the greater the poppet valve opening and corresponding fluid flow. The fluid pressure on the low-pressure side acts on the underside of the diaphragm applying an upward force. Obviously, the greater the pressure, the greater the upward force.
As such, the diaphragm""s deflection/poppet opening is dictated by a balance-of-forces. The range spring applies a downward force. The balancing upward forces are the outlet pressure acting on the diaphragm effective surface area, the bias spring, the diaphragm or spring force, and the inlet pressure acting on the poppet/seat area. This can be illustrated by the equation
Range Spring Force=Outlet Pressure Force+Bias Spring Force+Diaphragm Spring Force+Inlet Pressure Force 
A problem with conventional metal diaphragm regulators is that the diaphragms have a positive spring rate that contributes to a reduction in flow capacity. Flow capacity is the usable flow range of a pressure regulator without significant loss in outlet pressure. The higher the diaphragm spring rate, the greater the reduction in flow capacity.
The diaphragm deflection multiplied by the diaphragm spring rate equals the diaphragm spring force. As the diaphragm and poppet valve deflect downward, not only does flow increase, but also the diaphragm spring force increases, with the amount of change dependent upon its spring rate. As shown in the above xe2x80x98balance-of-forcesxe2x80x99 equation, an increase in diaphragm spring force contributes to a decrease in outlet pressure, resulting in a reduction of flow capacity.
This problem is further exasperated with a small or miniature metal diaphragm pressure regulator. Often it is desirable to use miniature metal diaphragm pressure regulators; however, what is not desirable is the extra reduction in flow capacity associated with the smaller size. Smaller diametrically sized diaphragms are less flexible, and they therefore typically have higher spring rates.
Examples of methods to reduce spring rates within a pressure regulator found in the art include U.S. Pat. Nos. 1,103,020 and 3,689,055. Although these help to reduce spring rates, they do so by requiring additional components, added complexity, and increased costs.
Another problem with conventional metal diaphragm regulators is that the diaphragm deflection and its associated poppet valve deflection is very small, particularly with smaller regulators, which limits the metering capability or controllability of the flow. The poppet valve as it deflects into or away from the valve seat changes the annular orifice area, thereby changing the flow. A greater deflection would allow for a finer and more controllable flow from the no-flow to full flow range. This would result in a smoother and more stable pressure control as flow demands change. To obtain the same flow range with a shorter deflection would result in a very xe2x80x98coarsexe2x80x99 flow control, resulting in a less stable pressure control.
Another problem with conventional metal diaphragm regulators is their low maximum inlet pressure rating. The maximum inlet pressure rating is primarily based on the weakest link, normally the thin metal diaphragm. Even though the diaphragm is located on the low-pressure side, the diaphragm must be able to hold without rupturing full inlet pressure with a suitable safety margin in the event of seat leakage. This is especially true in industries such as the semiconductor industry, where many of the gases that are pressure regulated are extremely hazardous (toxic, flammable, poisonous, pyrophoric, corrosive, etc.).
Metal diaphragms currently are designed to be as thin as reasonably possible so as to minimize the above-mentioned problems of high spring rate and short deflection. A thinner diaphragm has a lower spring rate and is typically able to deflect more. However, thinning out a diaphragm reduces its pressure holding capability.
While the inventions of the above-mentioned patents may be suitable for the particular purpose to which they address, they are not as suitable for increasing flow capacity, flow control, and pressure rating. Accordingly, there is a need for a metal diaphragm structure for pressure regulators that increases flow capacity, flow control, and pressure rating.
In view of the foregoing disadvantages inherent in known types of metal diaphragm regulators found in the art, the present invention provides a new metal diaphragm structure for pressure regulators construction that can be utilized for increasing flow capacity, flow control, and pressure rating. This metal diaphragm structure for pressure regulators substantially departs from the conventional concepts and designs of the prior art, and in so doing provides an apparatus primarily developed for the purpose of increasing flow capacity, flow control, and pressure rating.
The present invention generally includes a specially shaped metal diaphragm installed and clamped on its periphery into the outlet cavity of a pressure regulator body. The diaphragm is a circular thin metal disc dome shaped with specifically controlled height and thickness values.
The present invention further provides a metal diaphragm structure for pressure regulators that increases flow capacity, flow control, and pressure rating. The present invention also provides a metal diaphragm structure for pressure regulators that produces a non-positive spring rate throughout its usable deflection.
The metal diaphragm structure for pressure regulators of the present invention allows for a large deflection relative to its diametric size. The metal diaphragm structure of the present invention also utilizes a thick diaphragm material relative to its diametric size. Further, the metal diaphragm structure for pressure regulators according to the present invention increases flow capacity, flow control, and pressure rating without requiring additional components.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. Additional features of the invention will be described hereinafter.
It is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.